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APPENDIX                                  333
liquid with a mixture of concentrated sulphuric and nitric acids,
(p. 142;. The product is then poured into water. If the product
.sinks as a yellow liquid or solid it is prohablya nitro-compound
and the original hydrocarbon is aromatic. If it floats unchanged
on the surface of the water, it is probably a paraffin. An
aromatic hydrocarbon also dissolves in fuming sulphuric acid on
warming and shaking and does not separate on pouring the
solution into water. A paraffin is unacted on and separates on
the surface. There is also a marked difference in the smell of
the two classes of hydrocarbons.
Higher Alcohols and Phenol.—The substance will react
with metallic sodium yielding hydrogen, with phosphorus
pentachloride giving HC1. It can be identified by its
boiling point and by the b.p. or m.p. of the benzoic ester (p. 208).
In the case of a phenol it will possess a phenolic smell and may
give a, distinctive colour reaction with FeCla (p. 180).
Aldehydes   and  Kc tones.— The  usual   tests    are   applied
(P- 33°)-
Acids.— The number of liquid, insoluble acids is very limited
and is confined to the aliphatic series. They possess distinctive
b.p.'s and smells and dissolve readily in a solution of sodium
Ethers and Phenol Ethers have usually a pleasant odour
and if the methyl or ethyl ether is present are decomposed on
heating with strong hydriodic acid. The evolved gas passed into
alcoholic silver nitrate will give a precipitate as in Zeisel's method
(p. 220).
Kstcrs possess a fruity smell and usually distil without
decomposition. Boil with reflux for 5 minutes on the water-bath
a few c.c. of the liquid with 3 to 4 volumes of a ten per cent, solu-
tion of caustic potash in methyl alcohol and pour into water.
Notice if the liquid dissolves and has lost the odour of the ester.
An ester will be completely hydrolysed, and if the alcohol is
soluble in water a clear solution will be obtained. If the alco-
hol is volatile and the solution neutralised with sulphuric acid
and evaporated on the water-bath, the alkali salt of the organic
acicl mixed with potassium sulphate will be left and the acid
may be"investigated as described under §1. If it is required to
ascertain the nature of the alcohol in the ester, hydrolysis must
\g effected with a strong aqueous solution of caustic potash